In a so called diversity combining radio receiver, two or more received versions of the same transmitted signal are utilized in order to improve overall signal to noise ratio (SNR) and/or decrease distortion before demodulation (compared with using only a single version). In order for the diversity combining to be efficient in attaining such improvement, the noise and distortion of the two or more versions in the diversity signal branches to be combined should have low correlation, i.e. the branches should be diverse. Signal branch diversity can for instance be obtained in space by locating receiver antennas some distance apart, in frequency by using different carriers, or in antenna polarity. A distinction if often made between soft combining diversity and hard switching diversity. In the latter case, one of the received signals (the one deemed most “trustworthy”) is used for detection and the remaining signals are discarded. In soft diversity combining systems two or more received waveforms, henceforth denoted branches, are aligned in delay and phase, weighted according to their relative signal quality and coherently summed together before detection. Thus, there is a need for relatively accurate means for evaluating the signal quality of a diversity-combining radio receiver.